How a Fixed Hot Spot and a Moving Plate Built the Hawaiian Islands

The Hawaiian Islands were built by a volcano that stays in one place while the ground above it moves. The hot spot beneath them is fixed; the Pacific Plate slides over it. The result is a chain of islands and seamounts, each older than the one to its southeast.

A bathymetric map of the main Hawaiian Islands. Credit: U.S. Geological Survey.

Plates and hot spots

The Earth's outer crust is made of tectonic plates that move over the surface of the planet. Where plates come together, volcanoes sometimes form. But volcanoes can also form in the middle of a plate, where magma rises until it erupts on the seafloor. That place is called a hot spot.

A conveyor of islands

The Hawaiian Islands formed over a hot spot in the middle of the Pacific Plate. As the plate moved across it, the hot spot built a string of islands, one after another.

The Hawaiian-Emperor seamount chain is a well-known example of a seamount and island chain made this way. Each island or submerged seamount in the chain is older than the last, moving toward the northwest. Near Hawaii, the ages of the islands can be used to calculate how the Pacific Plate is moving toward the northwest. The youngest seamount in the chain, Loihi, is erupting from its summit at a depth of 1000 meters.

A vast archipelago

The Hawaiian Islands form an archipelago spread over a vast area of the North Pacific. It is made up of 132 islands, atolls, reefs, shallow banks, shoals and seamounts, stretching over 1,500 miles from the island of Hawaii in the southeast to Kure Atoll in the northwest.

Sources

Based on "How did the Hawaiian Islands form?" from NOAA's National Ocean Service, a work of the United States government in the public domain.